关于屏蔽系统热键的问题

Question

各位朋友，我在网上找了这样一段代码：
 #region Delegates        public delegate int HookProc(int nCode, Int32 wParam, IntPtr lParam);        #endregion        #region 变量声明        private HookProc KeyboardHookProcedure;        private FileStream MyFs; // 用流来屏蔽ctrl alt delete        private const byte LLKHF_ALTDOWN = 0x20;        private const byte VK_CAPITAL = 0x14;        private const byte VK_ESCAPE = 0x1B;        private const byte VK_F4 = 0x73;        private const byte VK_LCONTROL = 0xA2;        private const byte VK_NUMLOCK = 0x90;        private const byte VK_RCONTROL = 0xA3;        private const byte VK_SHIFT = 0x10;        private const byte VK_TAB = 0x09;        public const int WH_KEYBOARD = 13;        private const int WH_KEYBOARD_LL = 13;        private const int WH_MOUSE = 7;        private const int WH_MOUSE_LL = 14;        private const int WM_KEYDOWN = 0x100;        private const int WM_KEYUP = 0x101;        private const int WM_LBUTTONDBLCLK = 0x203;        private const int WM_LBUTTONDOWN = 0x201;        private const int WM_LBUTTONUP = 0x202;        private const int WM_MBUTTONDBLCLK = 0x209;        private const int WM_MBUTTONDOWN = 0x207;        private const int WM_MBUTTONUP = 0x208;        private const int WM_MOUSEMOVE = 0x200;        private const int WM_MOUSEWHEEL = 0x020A;        private const int WM_RBUTTONDBLCLK = 0x206;        private const int WM_RBUTTONDOWN = 0x204;        private const int WM_RBUTTONUP = 0x205;        private const int WM_SYSKEYDOWN = 0x104;        private const int WM_SYSKEYUP = 0x105;        private static int hKeyboardHook = 0;        #endregion        #region 函数转换        [DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]        public static extern int SetWindowsHookEx(int idHook, HookProc lpfn, IntPtr hInstance, int threadId);        //   卸载钩子          [DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]        public static extern bool UnhookWindowsHookEx(int idHook);        //   继续下一个钩子          [DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]        public static extern int CallNextHookEx(int idHook, int nCode, Int32 wParam, IntPtr lParam);        //   取得当前线程编号          [DllImport("kernel32.dll")]        private static extern int GetCurrentThreadId();        [DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]        private static extern short GetKeyState(int vKey);        #endregion        #region 方法        /// <summary>        /// 钩子回调函数，在这里屏蔽热键。
        /// <param name="nCode">The n code.</param>        /// <param name="wParam">The w param.</param>        /// <param name="lParam">The l param.</param>        /// <returns></returns>        private int KeyboardHookProc(int nCode, Int32 wParam, IntPtr lParam)
        {            KeyMSG m = (KeyMSG)Marshal.PtrToStructure(lParam, typeof(KeyMSG));                        if (((Keys)m.vkCode == Keys.LWin) || ((Keys)m.vkCode == Keys.RWin) ||                ((m.vkCode == VK_TAB) && ((m.flags & LLKHF_ALTDOWN) != 0)) ||                ((m.vkCode == VK_ESCAPE) && ((m.flags & LLKHF_ALTDOWN) != 0)) ||                ((m.vkCode == VK_F4) && ((m.flags & LLKHF_ALTDOWN) != 0)) ||                (m.vkCode == VK_ESCAPE) && ((GetKeyState(VK_LCONTROL) & 0x8000) != 0) ||                (m.vkCode == VK_ESCAPE) && ((GetKeyState(VK_RCONTROL) & 0x8000) != 0)                )
            {                return 1;            }
            return CallNextHookEx(hKeyboardHook, nCode, wParam, lParam);        }        
        /// 启动Hook，并用流屏蔽任务管理器        public void HookStart()
        {            if (hKeyboardHook == 0)
            {                //   创建HookProc实例                  KeyboardHookProcedure = new HookProc(KeyboardHookProc);                hKeyboardHook = SetWindowsHookEx(WH_KEYBOARD,                                                 KeyboardHookProcedure,                                                 Marshal.GetHINSTANCE(Assembly.GetExecutingAssembly().GetModules()[0]),                                                 0);                //   如果设置钩子失败                  if (hKeyboardHook == 0)
                {                    HookStop();                    //throw new Exception("SetWindowsHookEx   failedeeeeeeee.");                }                //用二进制流的方法打开任务管理器。而且不关闭流.这样任务管理器就打开不了                MyFs = new FileStream(Environment.ExpandEnvironmentVariables("%windir%\\system32\\taskmgr.exe"),                                      FileMode.Open);                byte[] MyByte = new byte[(int)MyFs.Length];                MyFs.Write(MyByte, 0, (int)MyFs.Length);            }        }
        /// <summary>        /// 卸载hook,并关闭流，取消屏蔽任务管理器。        /// <re>          /// </summary>        public void HookStop()
        {            bool retKeyboard = true;            if (hKeyboardHook != 0)
            {                retKeyboard = UnhookWindowsHookEx(hKeyboardHook);                hKeyboardHook = 0;            }            if (null != MyFs)
            {                MyFs.Close();            }
            if (!(retKeyboard))
            {
                throw new Exception("UnhookWindowsHookEx     failedsssss.");
            }
        }
        #endregion
        #region Nested type: KeyMSG        public struct KeyMSG
        {            public int dwExtraInfo;            public int flags;            public int scanCode;            public int time;            public int vkCode;        }        #endregion
我想问一下，在窗体中怎么调用这个API的方法的，在窗体的哪个事件里调用的呢。帮帮帮忙吧！